ENGINE | 936 in MODEL 963, 964 |
Location
Y637 | Engine brake solenoid valve |
W14.15-1152-76
The engine brake solenoid valve (Y637) is attached at the front side of the cylinder head from the outside, jutting out.
Task
The engine brake solenoid valve (Y637) has the task to apply an oil pressure during actuation to the hydraulic engine brake units.
Design
A | Oil duct |
Y637 | Engine brake solenoid valve |
W14.15-1143-81
Function
For a stopped engine the valve body of the engine brake solenoid valve (Y637) lies under the force of gravity on its downstop. The control oil passage to the oil duct (A) is open. Since there is no oil pressure applied at this point in time, no control oil flows in the direction of the hydraulic engine brake unit. If the engine is started oil pressure is applied to the valve body and pushes this against the upper stop. In this way the control oil passage to the oil duct (A) is closed off.
Activation of the engine brake
The engine management (MCM) control unit (A4) actuates the engine brake solenoid valve (Y637) just as soon as the driver activates one of the engine brake over the multifunction control lever. The energization of the coil inside causes the valve body to be pressed into the downstop. The now again opened control oil passage allows pressurized oil to pass over the oil duct (A) to the respective hydraulic engine brake units of the individual cylinder.
Deactivation of the engine brake
If the driver sets the multifunction control lever back into position 0 or the engine brake is deactivated, the coil is no longer energized - the valve body is pushed upwards. No more oil can flow over the oil duct (A) to the hydraulic engine brake units. The engine oil still present in the hydraulic engine brake unit flows over the control valve in it back into the oil circuit of the engine.